Waveguide attenuators for use in satellite/microwave communications are generally constructed using lossy dielectric fins positioned to penetrate into a waveguide parallel to the electric fields to reduce the energy level of a signal at the output of the attenuator. These fixed or flap type attenuators suffer from several drawbacks. For example, known variable attenuators are typically long and heavy, especially when made to be tunable. Further, because the lossy dielectric fins are suspended in the waveguide cavity, the fins can not be provided with a suitable heat-sink arrangement. As a result, power handling capabilities are substantially limited by poor thermal conductivity characteristics of the lossy dielectric fins which must absorb portions of both incident and reflected power signal to effect the desired attenuation. Thus, such attenuators can not be employed in high power applications.
In addition, these known attenuators only have a single state of operation. More specifically, the designs of these attenuators only permits attenuation at a single, predetermined value. Thus, a need exists for an attenuator which overcomes these deficiencies.